1. Field of the Invention
The present invention relates to a keep call back device for connecting a call from a called subscriber to a calling subscriber after connecting the call from the calling subscriber to the called subscriber.
2. Description of the Related Arts
Recently, there are increasing demands for higher information transmission speed. One of effective means for speeding up the transmission of information is telephone communication. Telephone communication has become essential in both public and private lives. In addition, various services utilizing telephone communication have widely spread. For example, such services include shopping over telephone lines and reservations for concert tickets, golf courses and hotel rooms over telephone lines. Such services allow a buyer to buy a merchandise or the like without visiting the shop.
Under such circumstances, it is expected that there will be an increase in communication cost for buyers. In order to save the communication cost for subscribers, various methods have been proposed.
For example, there is a method wherein a call is temporarily disconnected after the communication is established and the seller then calls back the buyer (call back method). Such a call back process allows the communication cost which is otherwise borne only by the buyer to be shared between the seller and the buyer.
In the case of telephone shopping, it is desired that sellers bear communication cost in order to improve their services. Then, services have been introduced wherein sellers register dedicated telephone numbers at the network side and are charged for calls from buyers to the dedicated telephone numbers.
Japanese unexamined patent publication (Kokai) No. H01-044659 discloses a telephone set having a call back function wherein the telephone number of a caller is stored at a called party and, during the call, a call is placed back to the caller over another communication channel. Such a telephone set is an invention effective in an ISDN (Integrated Services Digital Network) wherein the called party is notified of the telephone number of the caller when he or she receives the call and wherein a single telephone set can be connected to a plurality of communication channels.
In the method wherein the called terminal calls back the calling terminal after the established call is once released, the called subscriber must perform steps of temporarily disconnecting the call after confirming the telephone number of the calling subscriber and placing a call to the subscriber who has placed the first call using that telephone number. On the other hand, the subscriber who has placed the first call must wait for the call back for an indefinite period of time after the first call is disconnected.
The service of tolling a called party using a dedicated phone number for the called party is provided without confirming the calling subscriber. As a result, a subscriber who is not going to buy a product can illegally place a call. There is an additional problem in that the cost for the communication established as a result of such an illegal call is charged to the called subscriber.
The method described in Japanese unexamined patent publication No. H01-044659 has another problem in that it is effective only for networks such as ISDN networks wherein a single subscriber can be connected to a plurality of different communication channels and is not applicable to networks wherein a single subscriber can be connected to only one communication channel.